Brachytherapy involves a minimally-invasive method for radiation therapy of a tumor, e.g. a prostate carcinoma, a cervix carcinoma, a mammary carcinoma or a larynx carcinoma by means of internal radiation therapy or radiation treatment in a direct target region. To carry out the therapy one or more radiation sources is placed in the direct vicinity of the area to be radiation-treated. To introduce the radiation sources, what are referred to as applicators or guides are frequently used, which are apparatuses similar to a catheter which are introduced or implanted into the body close to the tumor or directly into the tumor tissue. The radiation sources, in what is referred to as temporary brachytherapy, can remain in the body temporarily, e.g. for a few minutes or hours, or in permanent brachytherapy over a longer period or for an unlimited time.
In order to determine the precise target position of the radiation sources, a computed tomography (CT) or magnetic resonance tomography (MRT) image of the region to be irradiated can be prepared for example prior to the therapy. With the aid of this dataset obtained the precise dose distribution in the target region is calculated on a radiation therapy planning system. The number and the positions of the applicators to be introduced and the radiation sources are determined with reference to the ideal dose distribution on or in the tumor. Dose planning means that the radiation is only applied in high doses where the tumor is located. Through this method the surrounding and in some cases very highly radiation-sensitive tissue is not unnecessarily irradiated and damage is minimized. In addition, by contrast with an external radiation therapy, the skin is not damaged since radiation therapy is from inside.
After a preliminary examination, dose planning and the procurement of the materials needed, the actual brachytherapy is carried out. For this purpose the patient is sedated or anesthetized in a sterile environment (OP) and the applicators are implanted. This can be done using 2D fluoroscopy. After successful checking of the position of the applicators the internal radiation treatment is carried out with the aid of radioactive radiation sources, so-called seeds, e.g. in the form of capsules of Cesium-137 between one and five mm long. In the so-called afterloading method, the seeds are introduced manually or automatically through the applicators into their target area, in stages if necessary. The radiation dose in the target area is calculated using the radiation intensity of the individual seeds to be expected, as well as the time that they are in the applicator or in the target area. When the predicted exposure time is reached, in the case of a temporary brachytherapy, the seeds and the applicators are removed again, if necessary in stages. The exposure time as well as the calculated applied dose can be documented.